Deflection coil



mmm

Aprifi 11955 L. M. LEEDS DEFLECTION COIL Filed Sept. 8, 1955 INVENTOR LAURANCE M. LEEDS,

United States Patent DEFLECTION COIL Laurance M. Leeds, Syracuse, N. Y., assignor to General Electric Company, a corporation of New York Application September 8, 1955, Serial No. 533,199

Claims. (Cl. 313-76) The present invention relates in general to coil structures and in particular to an improved configuration for deflection coils for cathode ray beams.

Deflection coils for cathode ray beams conventionally include side portions and end portions. The side portions are generally parallel to the axis of the cathode ray beam and current flow therethrough produces a component of force that is transverse to the axis of the beam which in turn causes a deflection of the beam. The end portions conventionally extend outward and current flow through the end turns produces a component of force axially directed and tending to defocus the beam. Such defocusing is tolerable in some systems, kinescope presentation of black and white television, for example, in view of the fact that a relatively large beam diameter is used, and also that defocusing is observed as a reduction in resolution.

However, in high precision deflection systems Where very small diameter beams are utilized, in which the size thereof must be maintained substantially constant over the entire deflection range of the beam, srnall defocusing aberrations are intolerable. In high precision systems such as those requiring color registration, it is customary and necessary to provide and annex focus correction to take care of the difference in beam path length as the beam is deflected. Such dynamic focus correction however (although substantially adequate for color kinescopes) is grosslyinsuflicient in the correcting of focusing aberrations, caused by the deflection coil in high precision systems employing a light valve of the Schlieren optical type. It has been found that by testing a large number of the best deflection coils available representative of the present state of the art and utilizing focus correction to obtain as perfect a spot as possible, that the 30 micron (1.2 thousandths of an inch) pencil beam required in a particular high precision system was defocused by anywhere from 200 to 800 percent by the action of the deflection coil. In this particular high precision system, it is essential that the diameter of the beam not change by more-than a fraction of its diameter; otherwise the light output would fall to substantially zero.

Accordingly, applicants invention is directed to an improved coil configuration in which limitations of the kind mentioned above are substantially eliminated.

Another object of the present invention is to provide an improved deflection coil structure and arrangement.

A still further object of the present invention is to pro vide improvements in electromagnetic deflection coil assemblies for cathode ray guns and cathode ray tubes.

The novel features which I consider to be characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation together with other objects and advantages thereof can best be understood by reference to the following description taken in connection with the accompanying drawings in which:

Figure 1 is a cross-sectional view of the improved coil 2,830,213 Patented Apr. 8, 1958 "ice 1 structure of my invention as applied to a cathode ray ray beam, applicant has provided a cylindrical collar support adapted to surround the neck of the cathode ray gun. Two pairs of deflecting coils are also provided on the surface of the support, coils of each pair lying generally on a transverse diameter through the support with each of the coils having a pair of linear coil sides arranged to extend length-wise along the surface of the neck of the gun. The said linear coil sides may be of any of the usual forms such as, for example, a continuous winding with a graded distribution of turns per unit angle,

-or a sectionalized winding in discrete bundles of any desired distribution. Each of the coils includes a pair of coil ends. These coil ends are arranged to extend outward from the neck of the gun and backward toward the coil sides and in spaced relationship with respect to the coil sides.

In Figure 1 there is shown an embodiment of the present invention as applied to a cathode ray tube. in this figure is shown a cathode ray tube 1 having a neck portion 2 and a base portion 3 which is adapted to supply an electron beam through the neck portion 2. Surrounding the neck portion is the deflection coil assembly 4.

Reference is now made to Figure 2 wherein there is shown a perspective view of the deflection coil assembly of Figure 1, simplified for purposes of setting forth the salient features of applicants invention.

the form of a cylinder adapted to fit around the neck of the tube 1 and extending over an appreciable portion thereof. Secondary cores 6 and 7 of a suitable magnetic tube with their centers on a vertical axis and two windings for vertical deflection, one located diametrically opposite the other with their centers on the horizontal axis. ever, for the sake of clarity only the top horizontal winding, denoted by the numeral 10, and the right vertical winding, denoted by the numeral 11, are shown. Also, each of these windings is indicated as comprising only two turns. Of course, it is understood that each of the windings may include many turns in any desired angular distribution.

Each of the coils 10 and 11 include respective parallel or side conductors 12 and 13, respectively, and corresponding end turns. The term end turn refers to all that portion of the windings other than the parallel conductors inside the cylindrical core. The end turns 14 leave the parallel conductors in a radial direction and substantially at right angles thereto and are then bent or extended back parallel to the axis on to the secondary core. The end turn crossings are conveniently made in the form of arcs and are placed close to the secondary cores as will be readily apparent by inspection of the In this figureis shown a main core 5 of suitable magnetic material in rawing of Figure 2 and by tracing the circuits of winding 10 and winding 11. Since the end turn crossings are made in a location back from the end of the coil, the flux associated therewith is far less effective in distorting the electron beam. Furthermore, the secondary cores tend to pull in and concentrate the desired flux. It should be understood that current flow in the coil sides 12 and 13 produces a magnetic field which is directed transverse to the axis of the core 5 in a direction to move the beam in the vertical and horizontal directions, respectively. The end turn crossings in normal conventional deflection coils, being at the ends of the outward extensions, have a strong eflect of introducing a component of magnetic force in the direction of the beam travel which results in a defocusing of the beam.

In accordance with applicants invention, the end turns have been disposed in a manner to minimize this action and thereby avoid the deleterious defocusing effects. Elfective operation may be had in extending the end turns outward from the axis of the core and backwards on to the side. However, more effective action is obtained when a core member such as the annular members 6 and 7 are located so as to concentrate the end turn flux. Inclusion of an air gap or other suitable gap between the annular members 6 and '7 and the core also serves to avoid contamination of the flux produced by the side or parallel conductors l2 and 13 with the end turn flux and further improves the operation of the deflection arrangement.

While cores have been shown, they may be conveniently eliminated if desired. It has been found that proper cnd turn configuration and core structure on that side of the assembly corresponding to the exit end of the electron beam is more critical than at the entrance end and conveniently this end alone may include the annular core. One reason for the greater importance attached to this end of the assembly is the fact that the beam from the exit end of the deflection coil is no longer on the axis of the assembly but rather is displaced therefrom in a direction closer to the end turns which then would have greater defocusing effect on the beam.

Although in the embodiment of Figure 2 I have shown the end turns brought off in a true radial fashion, this is convenient when the turns of the vertical and horizontal windings are interweaved and have the same axial length. When the vertical coils and the horizontal coils are made of different lengths, the radial portions can be directed so as to concentrate them and result in shorter crossing turns.

While a particular embodiment of my invention has been shown and described, it is apparent that changes and modifications may be made without departing from the invention in its broader aspects, and therefore the aim in the appended claims is to cover all such changes that fall within the true scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A sweep yoke assembly adapted to be fitted around the neck portion of a cathode ray gun, comprising two pairs of transverse deflecting coils, each coil having a symmetrical pair of linear coil sides arranged to extend lengthwise along the surface of said neck portion and a pair of coil ends, said coil ends extending substantially radially outward from said neck portion and backward substantially parallel to said respective sides and in spaced relationship with said sides.

2. A coil assembly comprising a coil having side portions and end portions, the portions of said coil turns comprising the side portion being substantially parallel and together defining a portion of a cylindrical surface, the end portions of said coils extending substantially radially outward from said cylinder and backward 'substantially parallel to said side portions and in spaced relationship with said side portions.

3.' A sweep yoke assembly adapted to be fitted around the neck portion of a cathode ray gun comprising two pairs of transverse deflecting coils, each including a plurality of coil sides arranged to extend lengthwise along the surface of said neck portion and a pair of coil ends, a cylindrical core member extending about said coils adjacent one end thereof, said coil portions extending substantially radially outward from said neck portion and backward substantially parallel to said core member.

4. An electromagnetic deflecting yoke structure for a cathode ray gun comprising a cylindrical core support member adapted to surround the neck of such tube, two pairs of deflecting coils lying on the surface of said support adjacent said neck, the coils of each pair aligned generally on a transverse diameter through said support, each of said coils having a pair of thin linear coil sides arranged to extend lengthwise along the surface of said neck and a pair of coil sides, said coil sides extending substantially radially outward from said neck portion and backward substantially parallel to said cylindrical core and in spaced relationship therewith.

5. An electromagnetic deflecting yoke structure for a cathode ray gun comprising a cylindrical core support adapted to surround the neck of such gun, two pairs of deflecting coils lying on the surface of said support adjacent said neck, the coils of each pair aligned generally on a transverse diameter through said support, each of said coils having a pair of linear coil sides arranged to extend lengthwise along the surface of said neck and a pair of coil ends, a pair of annular core members surrounding said core member and concentric therewith and located at respective ends of said core member and in spaced relationship therewith, said coil ends extending outward from said neck portion and backward toward said annular core member.

FOREIGN PATENTS 709,382 Great Britain May 19, 1954 Janssen Sept. 21, 19 54 

